Osteoporosis is a disease of bone in which the amount of bone is decreased and the strength of trabecular bone is reduced, cortical bone becomes thin and bones are susceptible to fracture.
It is estimated that 10 million Americans have established osteoporosis and another 34 million have osteopenia, or low bone mass, which leads to osteoporosis. The disease is responsible for 1.5 millions fractures annually, mostly involving the lumbar vertebrae, hip, and wrist.
Patients who are at risk for osteoporosis can be treated with vitamin D and calcium supplements. Bisphosphonates are also commonly used in the prophylaxis and treatment of osteoporosis and corticosteroid-induced osteoporosis. Bisphosphonates are synthetic analogues of natural pyrophosphate that inhibit osteoclast activity and decrease bone turnover and resorption.
The bisphosphonates alendronic acid and risedronate sodium are considered the drugs of choice for treatment of osteoporosis, but disodium etidronate may also be used. Treatment results in lower fracture rates and higher bone density in both male and female patients. Lifestyle changes are also generally prescribed for sufferers.
Whilst it is known to treat osteoporosis with bisphosphonates, there are a number of gastrointestinal symptoms associated with this class of drugs such as abdominal pain, dyspepsia, diarrhoea or constipation. Severe gastrointestinal reactions and oesophageal reactions such as oesophagitis, erosions, and ulceration have occurred. As a consequence biphosphonates should not be administered to patients with abnormalities of the oesophagus or other factors that might delay oesophageal emptying, or those unable to stand, or sit upright for at least 30 minutes (Martindale). Strict instructions are set out for taking these drugs, patients taking alendronate are instructed to take it on an empty stomach before food and to remain sitting upright without eating for at least 30 minutes after taking the drug. Similar instructions, in some case stricter, apply for other bisphosphonates.
The reason for these instructions is that alendronate and other bisphosphonates can provoke severe oesophageal irritation. This can lead to reflux into the oesophagus and consequent ulceration, oesophagitis, heartburn and retrosternal pain, pain on swallowing and dysphagia. In addition to these side-effects, there is reduced patient compliance with the bisphosphonate treatment, leading to progression of the osteoporosis.
Bisphosphonate treatment is so effective that it is very widely used. Patients have hitherto had to put up with the adverse symptoms associated with bisphosphonate use as there is no alternative treatment that gives such good results.
An object of the invention is to ameliorate the above problems and disadvantages. An object of a specific embodiment of the invention is to provide a formulation of a bisphosphonate which provokes reduced gastric irritation and/or reduced reflux of stomach acid, leading preferably to increased patient compliance.